The invention lies in the field of flight management systems (termed “FMS”) and ATC (“Air Traffic Control”, that is to say air traffic management) communications between aircraft and management control stations on the ground.
The growing proportion of automation over the last twenty-five years in avionics, both civil and military, is leading aircraft crews ever more to perform “monitoring” tasks in regard to electronic systems, and ever less to directly influence the primary piloting controls of aircraft.
This trend has become accentuated over the last fifteen years with the generalization of onboard flight management systems (FMS).
These systems concentrate a large amount of data:
                arising from sensors (GPS, VHF) for navigation,        arising from databases (navigation databases) for formulating the electronic flight plan,        arising from performance databases for formulating the predictions along the flight plan,        arising from manual inputs on the part of the crew (in general for initializing the calculations) or automatic inputs by “datalink” (ground-air digital data link) coming from the airline or air traffic control centers (ATC).        
Among the pilot's tasks, the management of the flight directives received from the ATC, subsequently dubbed “clearances”, occupies a very significant proportion of the job. The clearances coming from the ground can be taken into account on board in two ways:                either directly, via the flight controls or the automatic pilot,        or via a flight management computer (FMS). In the latter case, according to the current state of the art, the pilot manually modifies his flight plan so as to take account of a clearance originating from the ground.        
This way of proceeding may potentially generate problems of oversights and confusion. Moreover, when the crew, having accepted a certain number of clearances from the ground, and modified the flight plan accordingly, receives a clearance to cancel one of the directives, it is almost impossible for the crew to actually remove this clearance from the flight plan.
In a more automated ATM framework, this is prohibitive in respect of both safety and operational use of the possibilities offered by the datalink. The pilot cannot reverse his flight plan (no multiple “UNDO”) if the latest clearances received and loaded for testing into his FMS are not suitable for him, and he cannot cancel an intermediate instruction either.